1X fired 6 Dasher brass not sealing

[marine52]

With .007 clearance, the neck may not be sealing well allowing carbon to get to the shoulder. That is more clearance than I would be comfortable with.

Agree. What you are seeing is a sign of too much clearance between the case neck and chamber. Read what @Webster said above. I’ve seen .2725 as no turn. .275 seems excessive. Ask your gunsmith.

 

[243winxb]

"Modular Sizing die Alpha Dasher is intended for chambers reamed with the Alpha Legacy reamer specs with utilizes a .0750 Neck / Shoulder radius and a .0300 Body Shoulder Radius."

OR

"The Modular Sizing Die for Dasher works with rifles chambered using a .060″ neck/shoulder radius and a .000″ shoulder/body radius reamer."

Yes, its Alpha brass.

Manson Reamers' Alpha reamer (spec order) neck dimension is 0.275".

I dont see a SAAMI standard for 6 mm Dasher?

 

[TackDriv3r]

More neck tension might allow the pressure to build higher before the bullet leaves the neck giving a better seal? I use a .265" bushing with a 0.125" thick neck.

I have loaded 3 cases tonight after annealing on the 2X fired cases, used .265 bushing without the mandrel and its .005" off the lands.
Other 6 is the same charge with 31.8 grains to yield 2940 fps, 3 of the 6 is .010" jam with .001" neck tension, the 2nd 3 is .005" off. Let me try those out and hopefully see something positive.

 

[TackDriv3r]

"Modular Sizing die Alpha Dasher is intended for chambers reamed with the Alpha Legacy reamer specs with utilizes a .0750 Neck / Shoulder radius and a .0300 Body Shoulder Radius."

OR

"The Modular Sizing Die for Dasher works with rifles chambered using a .060″ neck/shoulder radius and a .000″ shoulder/body radius reamer."


Manson Reamers' Alpha reamer (spec order) neck dimension is 0.275".

I dont see a SAAMI standard for 6 mm Dasher?
View attachment 1668858

I believe the gunsmith used an Alpha reamer and no turn is .275. On a few fired brass I have measured the OD of the necks, it shows .274" with some springback, should be a .275".
If I had known that there would be .007" clearance, i would have asked for a .272" no turn since I have .268 loaded neck.

 

[TackDriv3r]

Shims- .001" to .025"
Looks like another way to adjust the shoulder bump??
View attachment 1668837

It's at .002" shoulder bump. Fired brass was at 1.193" using SAC headspace, and after sizing its 1.191"
Also tried .1.192" and closed bolt, and I feel little resistance, so I tried the 1.191" and no resistance.

 

[JFrank]

Here’s some additional material.

Thread '6 Dasher reamer for Alpha brass'

Mar 22, 2024

I have a customer wanting a barrel chambered for 6 Dasher. He has purchased Alpha brass. His loaded neck diameter is 0.270".
Manson lists a std reamer with 0.2725" neck and Alpha reamer (spec order) with 0.275" neck. Do you think the std reamer neck will give problems without turning brass?

• Dave in WI
• Replies: 36
• Forum: 6BR, 6BR Improved & Wildcats

• 

 

[littlebuddybr]

Nope..
The only time I personally use one is to relax brand new un-fired brass necks, after that first time I haven’t found the need.

Not advising , just sharing..

Jim

This has been my experience as well.

 

[243winxb]

There would seem to be 2 different Neck/shoulder Bushings?

Alpha Legacy reamer specs with utilizes a .0750 Neck / Shoulder radius and a .0300 Body Shoulder Radius."

The Modular Sizing Die for Dasher works with rifles chambered using a .060″ neck/shoulder radius and a .000″ shoulder/body radius reamer.

Need the correct neck/shoulder bushing for the Alpha Brass?

"Note: These Dasher Bushings are for chambers with a .060″ Neck / Shoulder Radius and a .000″ Shoulder / Body Radius. Not Alpha Legacy ® Chambers."

Dasher – Neck/Shoulder Bushings

*** These bushings are proprietary to Short Action Customs Modular Sizing Dies only! They will not work with any other die *** Note: These Dasher Bushings are for chambers with a .060" Neck / Shoulder Radius and a .000" Shoulder / Body Radius. Not Alpha Legacy ® Chambers.

shortactioncustoms.com

Correct bushing for Alpha Dasher-

Alpha Dasher – Neck/Shoulder Bushings

*** These bushings are proprietary to Short Action Customs Modular Sizing Dies only! They will not work with any other die *** Note: "Alpha Dasher" bushings are specific to rifles chambered with Alpha Munitions Reamers. Only select "Alpha Dasher" if your rifle has an Alpha Dasher chamber.

shortactioncustoms.com

"Note: “Alpha Dasher” bushings are specific to rifles chambered with Alpha Munitions Reamers. Only select “Alpha Dasher” if your rifle has an Alpha Dasher chamber."

 

[TackDriv3r]

There would seem to be 2 different Neck/shoulder Bushings?


Need the correct neck/shoulder bushing for the Alpha Brass?

"Note: These Dasher Bushings are for chambers with a .060″ Neck / Shoulder Radius and a .000″ Shoulder / Body Radius. Not Alpha Legacy ® Chambers."

Dasher – Neck/Shoulder Bushings

*** These bushings are proprietary to Short Action Customs Modular Sizing Dies only! They will not work with any other die *** Note: These Dasher Bushings are for chambers with a .060" Neck / Shoulder Radius and a .000" Shoulder / Body Radius. Not Alpha Legacy ® Chambers.

shortactioncustoms.com

Correct bushing for Alpha Dasher-

Alpha Dasher – Neck/Shoulder Bushings

*** These bushings are proprietary to Short Action Customs Modular Sizing Dies only! They will not work with any other die *** Note: "Alpha Dasher" bushings are specific to rifles chambered with Alpha Munitions Reamers. Only select "Alpha Dasher" if your rifle has an Alpha Dasher chamber.

shortactioncustoms.com

"Note: “Alpha Dasher” bushings are specific to rifles chambered with Alpha Munitions Reamers. Only select “Alpha Dasher” if your rifle has an Alpha Dasher chamber."

Yes, I have the Alpha Dasher bushings. My chamber was cut with an Alpha reamer.

 

[243winxb]

Magnum small rifle primer being used?

Neck tension/bullet hold- The outside neck diameter should expand a minimum of .002" after bullet seating.

I'M still guessing .

 

[Webster]

More neck tension might allow the pressure to build higher before the bullet leaves the neck giving a better seal? I use a .265" bushing with a 0.125" thick neck.

If your gun smith gave you a .275" chamber neck you need a new gunsmith. All the top shooters use a no turn 0.002" neck tension, a few .003".

 

[SS GO DEVIL]

Sounds to me like the shoulders are not being bumped correctly (too much in this case)
I would remove the bolt from the gun, remove entire firing pin, spring and bolt shroud from bolt. Carefully remove the ejector from the bolt (careful not to let spring shoot across room).

Now you can take a fired piece of brass and start slowly in small increments size the brass till the bolt just barely falls under it own weight with the sized brass in chamber. Use a shoulder bump gauge to record that measurement. Add .001 of additional bump to insure clearance. This method has worked best for me. This method uses the guns chamber for your measurement tool instead of shoulder bump gauge. Sometimes the gauges/dies don't match the chamber exactly. What's also cool about this method is once the die is set this way you can lock the ring down and never have to fool with it again (if you anneal often).

 

[SS GO DEVIL]

MY SPECS AS FOLLOWS:

.272 PTG NO TURN 6 DASHER .104 FREEBORE
ALPHA/LAPUA BRASS
6 DASHER WHIDDEN BUSHING FULL LENGTH DIE
.266 TiNi BUSHING
.241 MANDREL
CCI BR4
BERGER 105 VLD (JAM) 108BT (SMALL JUMP)
ANNEAL EVERY FIRING
TRIM EVERY FIRING
UNIFORM PRIMER POCKET EVERY FIRING

 

[urbanrifleman]

6xc Tubb chamber is .277" neck I think? It's won some stuff. Works just fine.

 

[243winxb]

carbon on the shoulders

Has the reason been found? Update?

 

[TackDriv3r]

Has the reason been found? Update?

I haven't had time to try a few tests yet, thinking to go this evening or tomorrow.

 

[JFrank]

I have loaded 3 cases tonight after annealing on the 2X fired cases, used .265 bushing without the mandrel and its .005" off the lands.
Other 6 is the same charge with 31.8 grains to yield 2940 fps, 3 of the 6 is .010" jam with .001" neck tension, the 2nd 3 is .005" off. Let me try those out and hopefully see something positive.

Why would 2x fired brass require annealing ?

 

[NZ_Fclass]

I believe that Manson have a reamer for Alpha Dasher chambers. Might be worth checking the size that Alpha recommend. Or simply talk to Alpha.

 

[TackDriv3r]

Why would 2x fired brass require annealing ?

I usually anneal after every firing? Why did you ask?

 

[Clancy]

If your gun smith gave you a .275" chamber neck you need a new gunsmith. All the top shooters use a no turn 0.002" neck tension, a few .003".

I’d much rather have .007 clearance than .002 clearance with a no turn chamber.

Clearance is your friend. The phrase “turn them thin to win” comes to mind.

I’ve shot literal, witnessed, verified .0s with leftover brass turned to .264 in a .272 chamber.

.004 may be ideal, but I’m not scared of .006. The next batch of Alpha might be .270-.271 loaded. Even with Lapua, there’s no guarantee on what it’ll measure.